U.S. patent application number 09/466911 was filed with the patent office on 2002-01-31 for ink jet head and ink jet recording apparatus having same.
Invention is credited to SAIKAWA, HIDEO.
Application Number | 20020012034 09/466911 |
Document ID | / |
Family ID | 26503296 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012034 |
Kind Code |
A1 |
SAIKAWA, HIDEO |
January 31, 2002 |
INK JET HEAD AND INK JET RECORDING APPARATUS HAVING SAME
Abstract
An ink jet head for ejecting ink includes an ink passage for
supplying ink from an ink container for containing ink; a filter
chamber in the ink passage, the filter chamber containing therein a
filter; wherein the chamber has a cross-sectional area larger than
that of the ink passage, and is provided with an inlet opening in
fluid communication with an inlet part of the ink supply passage
for supplying the ink from the ink container to the filter chamber
and an outlet opening in fluid communication with an outlet part of
the ink passage for supplying the ink out of the chamber; wherein
the inlet opening and outlet opening are faced to a filter with a
clearance, and the chamber is provided with bubble moving portion
for moving bubbles away from the inlet opening.
Inventors: |
SAIKAWA, HIDEO; (TOKYO,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112-3801
US
|
Family ID: |
26503296 |
Appl. No.: |
09/466911 |
Filed: |
December 20, 1999 |
Current U.S.
Class: |
347/93 |
Current CPC
Class: |
B41J 2/17513 20130101;
B41J 2/17523 20130101; B41J 2/17563 20130101; B41J 2/19 20130101;
B41J 2002/14403 20130101 |
Class at
Publication: |
347/93 |
International
Class: |
B41J 002/175 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 1993 |
JP |
219457/1993 |
Aug 8, 1994 |
JP |
185746/1994 |
Claims
What is claimed is:
1. An ink jet head for ejecting ink, comprising: an ink passage for
supplying ink from an ink container for containing ink; a filter
chamber in said ink passage, said filter chamber containing therein
a filter; wherein said chamber has a cross-sectional area larger
than that of said ink passage, and is provided with an inlet
opening in fluid communication with an inlet part of said ink
supply passage for supplying the ink from said ink container to
said filter chamber and an outlet opening in fluid communication
with an outlet part of said ink passage for supplying the ink out
of said chamber; wherein said inlet opening and outlet opening are
faced to a filter with a clearance, and said chamber is provided
with bubble moving means for moving bubbles away from the inlet
opening.
2. An ink jet head according to claim 1, wherein said bubble moving
means provides a smallest clearance between said filter and an
internal wall of said chamber adjacent the inlet.
3. An ink jet head according to claim 1, wherein said bubble moving
means is in the form of a recess in an internal wall surface of
said chamber away from the inlet opening.
4. An ink jet head according to claim 1, wherein said air moving
means is in the form of an internal wall surface of said chamber
having a better wettability adjacent the inlet opening than a
portion away therefrom.
5. An ink jet head according to claim 1, wherein said air moving
means is in the form of an internal wall surface of said chamber or
said filter inclined relative to a horizontal plane.
6. An ink jet head according to claim 1, wherein said ink jet head
comprises an electrothermal transducer element for ejecting the
ink.
7. An ink jet recording apparatus, comprising: an ink jet head for
ejecting ink; an ink passage for supplying ink from an ink
container for containing ink; a filter chamber in said ink passage,
said filter chamber containing therein a filter; wherein said
chamber has a cross-sectional area larger than that of said ink
passage, and is provided with an inlet opening in fluid
communication with an inlet part of said ink supply passage for
supplying the ink from said ink container to said filter chamber
and an outlet opening in fluid communication with an outlet part of
said ink passage for supplying the ink out of said chamber; wherein
said inlet opening and outlet opening are faced to a filter with a
clearance, and said chamber is provided with bubble moving means
for moving bubbles away from the inlet opening.
8. An ink jet recording apparatus according to claim 7, wherein
said bubble moving means provides a smallest clearance between said
filter and an internal wall of said chamber adjacent the inlet.
9. An ink jet recording apparatus according to claim 7, wherein
said bubble moving means is in the form of a recess in an internal
wall surface of said chamber away from the inlet opening.
10. An ink jet recording apparatus according to claim 7, wherein
said air moving means is in the form of an internal wall surface of
said chamber having a better wettability adjacent the inlet opening
than a portion away therefrom.
11. An ink jet recording apparatus according to claim 7, wherein
said air moving means is in the form of an internal wall surface of
said chamber or said filter inclined relative to a horizontal
plane.
12. An ink jet recording apparatus according to claim 7, wherein
said ink jet head comprises an electrothermal transducer element
for ejecting the ink.
Description
FIELD OF THE INVENTION AND RELATED ART
[0001] The present invention relates to an ink jet head for
ejecting ink to effect recording, and an ink jet recording
apparatus provided with the same, more particularly it relates to
an ink supply system in an ink jet head.
[0002] An ink jet recording apparatus is provided with a recording
head (ink jet head) having a plurality of ejection outlets
(nozzles) for ejecting the ink. If the ejection outlet is clogged,
normal recording is not possible.
[0003] An improper ejection due to the clogging at the ejection
outlets occurs, for example, due to fine foreign matters introduced
from an ink supply system when an ink container for containing ink
having porous material to retain the ink therein, is exchanged, due
to the foreign matter produced from the recording material or the
like directly attached to the ejection side surface of the ink jet
head, or due to the high viscosity ink resulting from evaporation
of the ink solvent adjacent the ejection outlet when the recording
apparatus is kept unused for a long period.
[0004] For this reason, the provision of means for removing foreign
matters from the ink in a path from an ink accommodator to an
ejection outlet, is desirable. A general method therefor is the
provision of a filter in the ink supply path to remove the foreign
matter.
[0005] As a method for preventing the clogging of the ejection
outlets due to the external foreign matters, a widely used method
is a recovery process in which the ink is sucked through the ink
ejection outlet to suck the foreign matters out.
[0006] The sucking recovery process is advantageous because it can
remove fine bubbles in a common liquid chamber or the like with
which the plurality of ejection outlets are in fluid communication,
as well as the foreign matters adjacent the ejection outlet. If the
bubbles exists in the common liquid chamber or the like, the
ejection pressure is undesirably reduced.
[0007] When the filter is used, the bubbles in the ink supply path
are moved with the supply of the ink from the ink accommodator to
the recording head with the ink to the filter, so that they are
concentrated on the filter. When the recording head and an ink
cartridge is detachably mountable together, the air may be
introduced upon the coupling of the recording head and the ink
cartridge. The bubbles may be produced by the solved air in the ink
by ambient condition change or the like. The bubbles concentrated
on the filter may obstruct ink flows through the filter or clogs
the filter intermittently to make the ink supply instable. To avoid
this, the sucking recovery device for removing the above-described
clogging is also utilized as the mechanism for removing the bubbles
from the filter.
[0008] The ink jet apparatus is used in many fields, and therefore,
it is desirable that the ink jet unit comprising the ink jet head
or an ink cartridge as an ink accommodator therefor, is made common
for the apparatuses in the different fields. An ink jet unit is
therefor desirable if the high quality image can be provided
irrespective of the position or pose of the ink jet unit without
the influence of the bubbles on the filter.
[0009] Recently, a high speed recording is desired in the ink jet
recording apparatus. For increasing the speed, the amount of ink
supply per unit type to the nozzle is to be increased.
[0010] In this case, if the cross-sectional area of the filter is
the same, the flow rate through the filter increases with the
result of increased flow resistance by the filter. As a result, the
ink supply would not be enough to meet the ejection cycle of the
high speed recording, and therefore, the ink ejection is not proper
with the result of deteriorated printing quality.
[0011] In order to assure the ink supply to the nozzle upon the
high speed recording in a small size ink jet apparatus, the portion
having the filter is enlarged beyond the inside diameter of the ink
passage to permit use of larger area of the filter, and therefore,
to avoid the increase of the ink flow rate per unit area so as to
avoid the increase of the flow resistance.
[0012] However, the increase of the effective area of the filter to
permit the high speed recording, means that the flow rate per unit
area is reduced as compared with that in the ink passage for the
purpose of suppressing the increase of the flow resistance.
Therefore, even if it is proper for the high speed recording, at
the time of the bubble removal by the recovery process, the ink
flow during the recovery operation is not enough to pass the
bubbles through the filter, in other words, the pressure diferences
across the filter is not sufficiently applied to the filter
portion. As a result, the difficulty arises in removing the bubbles
from the filter. Therefore, the air bubbles stagnate in the
filter.
[0013] In addition, with the above-described structure, the bubbles
flow with the ink toward the filter, and therefore, they are caught
at the central portion of the filter by the meniscus force. The
pressure of the ink flowing through the ink passage is much higher
during the recovery process operation as compared with the
recording operation. The pressure applied to the bubbles is also
high during the recovery processing operation, and therefore, the
change of the configuration of the bubbles on the filter is large
and complicated.
[0014] When the bubbles have a substantially large size, the
effective area of the filter reduces with the result of the
increased ink flow per unit area during the recovery operation, and
therefore, the pressure applied to the bubble is increased. As a
result, the pressure applies to the bubbles significantly and
locally changes.
[0015] Then, only a part of the bubbles is intermittently subjected
to a pressure beyond a threshold of passage through the filter with
the result of formation of fine bubbles. In addition, the position
of the pressure application locally changes because the bubble can
be freely deformed, the fine bubbles are further produced.
Particularly when the ink flows along the gravity, that is,
downwardly, the changes of the bubbles are promoted by the buoyancy
so that the production of the fine bubbles is promoted.
[0016] When the ink contains surfactant or the like effective to
promote the bubble formations, a part of the bubbles stagnating in
the filter is easily passed through the filter during the sucking
operation with the result of the fine bubbles remaining in the
liquid chamber of the recording head. Such fine bubbles in the
liquid chamber are adversely influential to the ink ejection.
[0017] The fine bubbles can be removed usually by the sucking
recovery operation. However, as described above, a part of the
bubbles passes through the filter with the result of fine bubble
production, and therefore, the removal of the fine bubbles from the
liquid chamber is difficult. It would be considered that the
bubbles on the filter are removed by using a larger capacity pump
for the sucking recovery. However, this results in the bulkiness of
the ink jet recording apparatus, against the recent demand.
SUMMARY OF THE INVENTION
[0018] Accordingly, it is a principal object of the present
invention to provide an ink jet recording head and an ink jet
recording apparatus with which a high speed recording is possible
without increasing the size of the ink jet recording apparatus with
simple and inexpensive manner, and in which the influence of the
bubbles stagnating at the filter is minimized.
[0019] It is another object of the present invention to provide an
ink jet recording head and an ink jet recording apparatus and an
ink jet recording method in which the bubbles stagnating at the
filter are not reformed into fine bubbles by a recovery process
such as sucking.
[0020] It is a further object of the present invention to provide
an ink jet recording head, an ink jet recording apparatus and an
ink jet recording method with which the adverse influence of the
bubbles stagnating at the filter is suppressed to permit stabilized
ejection, with a plurality of ejecting poses.
[0021] According to an aspect of the present invention, there is
provided an ink jet head for ejecting ink, comprising: an ink
passage for supplying ink from an ink container for containing ink;
a filter chamber in the ink passage, the filter chamber containing
therein a filter; wherein the chamber has a cross-sectional area
larger than that of the ink passage, and is provided with an inlet
opening in fluid communication with an inlet part of the ink supply
passage for supplying the ink from the ink container to the filter
chamber and an outlet opening in fluid communication with an outlet
part of the ink passage for supplying the ink out of the chamber;
wherein the inlet opening and outlet opening are faced to a filter
with a clearance, and the chamber is provided with bubble moving
means for moving bubbles away from the inlet opening.
[0022] In a second aspect of the present invention, there is
provided an ink jet head according to the first aspect, wherein the
bubble moving means provides a smallest clearance between the
filter and an internal wall of the chamber adjacent the inlet.
[0023] In a third aspect of the present invention, there is
provided an ink jet head according to the first aspect, wherein the
air moving means is in the form of an internal wall surface of the
chamber having a better wettability adjacent the inlet opening than
a portion away therefrom.
[0024] In a fourth aspect of the present invention, there is
provided an ink jet head according to the first aspect, wherein the
air moving means is in the form of an internal wall surface of the
chamber or the filter inclined relative to a horizontal plane.
[0025] In a fifth aspect of the present invention, there is
provided an ink jet recording apparatus, comprising: an ink jet
head for ejecting ink; an ink passage for supplying ink from an ink
container for containing ink; a filter chamber in the ink passage,
the filter chamber containing therein a filter; wherein the chamber
has a cross-sectional area larger than that of the ink passage, and
is provided with an inlet opening in fluid communication with an
inlet part of the ink supply passage for supplying the ink from the
ink container to the filter chamber and an outlet opening in fluid
communication with an outlet part of the ink passage for supplying
the ink out of the chamber; wherein the inlet opening and outlet
opening are faced to a filter with a clearance, and the chamber is
provided with bubble moving means for moving bubbles away from the
inlet opening.
[0026] According to an aspect of the present invention, the bubbles
stagnating at the filter moves toward the marginal portions in a
chamber where the filter is provided, and therefore, the obstruct
against the ink flow from the ink container can be prevented.
[0027] In an aspect of the present invention, the influence of the
variation of the ink supply pressure due to the configuration or
the like of the ink passage can be minimized.
[0028] Therefore, the formation of the fine bubbles at the filter
can be reduced.
[0029] Therefore, a high quality image recording is possible at all
times without reduction of the ink supply performance resulting
from the variation of the ink supply amount, in a high speed
recording.
[0030] These and other objects, features and advantages of the
present invention will become more apparent upon a consideration of
the following description of the preferred embodiments of the
present invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a perspective view of an exemplary ink jet
recording apparatus to which the present invention is
applicable.
[0032] FIG. 2 is an enlarged perspective view of a carriage of an
ink jet recording apparatus shown in FIG. 1.
[0033] FIG. 3 is perspective views of an ink jet head to which the
present invention is applicable, and (a) is a perspective view as
seen from an ink inlet side of the ink jet head, and (b) is a
perspective view as seen from a nozzle side.
[0034] FIG. 4 is a sectional view of an ink jet recording apparatus
according to a first embodiment of the present invention, and
illustrates an ink supply system from an inside of the ink
container or an ink accommodator to an end of the nozzles of the
ink jet head.
[0035] FIG. 5 is enlarged sectional views adjacent a filter of the
ink jet recording apparatus according to the first embodiment,
wherein various configurations of a filter box are shown.
[0036] FIG. 6 is a sectional view of an ink supply system from an
inside of an ink container to an end of the nozzles of the ink jet
head in an ink jet recording apparatus according to a second
embodiment of the present invention, in which (a) shows the case in
which the ink ejecting direction is substantially parallel with the
direction of the gravity, and (b) shows the case in which the
ejecting direction is substantially orthogonal to the direction of
the gravity.
[0037] FIG. 7 is an enlarged sectional view of a filter of an ink
jet recording apparatus according to a modification of the second
embodiment.
[0038] FIG. 8 is an enlarged sectional view of the filter in an ink
jet recording apparatus according to a third embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Referring to FIG. 1, there is shown an example of an ink jet
recording apparatus to which the present invention is applicable.
In FIG. 1, designated by reference numeral 1 is a carriage; 2, a
recording head (ink jet head); and 3, container guide. The ink jet
head and the container guide 3 are mounted on a carriage 1. To the
container guide 3, a color ink container 10 and a black ink
container 11 (ink accommodators) are mounted to supply the ink to
the ink jet head 2.
[0040] The ink container is detachably mountable on the container
guide 3, and are replaceable independently in accordance with the
respective ink consumptions. In this embodiment, the color ink
container 10 has a casing and cyan, magenta, yellow containers
therein. The ink chambers are separated by partition walls to
isolatedly accommodate the respective inks.
[0041] Designated by reference numeral 4 is a lead screws
interrelated with an unshown carriage motor; 5, a guide shaft. The
carriage 1 translate on the guide shaft 5 by the lead screw 4 to
scan the recording head over the recording material.
[0042] During the recording operation, the ink is ejected in the
direction of the gravity, that is, downwardly, from the ink jet
head 2. The ejected ink is received by the recording sheet 6
disposed faced to the ink ejection parts of the ink jet head 2, so
that an image is formed. The downward ink ejection is preferable
from the standpoint of the high speed recording because it promotes
the ink supply to the ink jet head after the ink ejection. The
recording sheet 6 is discharged in interrelation with the printing
action by a feeding roller 7, a discharging roller 8 and a sheet
confining plate 9.
[0043] FIG. 2 is an enlarged perspective view of the carriage 1
shown in FIG. 1, in which the container guide 3 has been removed
from the carriage 1. The color ink container 10 and the black ink
container 12 are mounted from a rear side which is opposite from
the ejection side of the ink jet head 2.
[0044] FIG. 3 is a perspective view of an ink jet head of FIG. 2.
In FIG. 3(a), the ink jet head is shown as seen from an ink inlet
side to the recording head (pipe side), that is, as seen from the
ink container insertion side, and FIG. 3(b) is a perspective view
as seen from the ejection side.
[0045] In FIG. 3(a), designated by a reference numeral 201 is a
silicon substrate on which heater or the like for the ink ejection
is formed; and 202, a print board including a driving circuit for
the ink jet head 2. Reference numeral 203 designates an aluminum
plate supporting the silicon substrate 201, the print board 202;
204, 205 and 206, ink supply pipes for supplying the yellow, cyan
and magenta inks from the color ink container 10 to the ejecting
parts of the respective colors through a unit 208.
[0046] In FIG. 3(b), designated by 2Y, 2M, 2C and 2BK are groups of
nozzles (ejection outlets) for ejecting yellow, cyan, magenta and
black inks, respectively. In the ink jet recording head 2, the
respective color nozzles are arranged on the respective lines.
[0047] Designated by a reference numeral 207 is an ink pipe for
introducing the ink from the black ink container 11, and is
disposed across the aluminum plate 203 from the ink pipe for the
color ink, shown in FIG. 3(a).
[0048] Embodiment 1
[0049] Referring to FIG. 4, a first embodiment is illustrated, in
which an ink jet head 2 and a color ink container 10 are connected.
A color ink supply system shown in FIG. 4 comprises an ink
container for containing the yellow ink, an ink passage for the ink
and ink ejection part and so on. Along the ink supply path, the
cross-sections are shown. Basically the same structure is used for
the other color ink supply system (black, magenta, cyan).
[0050] In FIG. 4, the silicon substrate 201 has energy generating
elements (not shown), and the nozzles 215 are at the ends of the
ink passages containing the energy generating elements. The ink 12
is ejected to the recording sheet 6 by the energy generated by the
energy generating element, from the nozzle 215. Thereafter, the ink
is supplied to the ink passage from the ink container.
[0051] In the color ink container 10, there is an ink absorbing
material 301Y for retaining the ink, the absorbing material being
of porous material or the like. By the capillary force provided by
the ink meniscuses formed in the pores of the ink absorbing
material 301Y, the pressure of the ink in the nozzle 215 is
maintained at a static negative pressure.
[0052] The negative pressure is a back pressure against the ink
supply to the ejection part of the ink ejecting head. It means a
static pressure lower than the ambient pressure at the ejection
part. In this embodiment, it is approx. -50 Pa relative to the
ambient pressure at the ejection part. Hereinafter, this is called
"negative pressure state".
[0053] The ink is retained in the ink absorbing material 301. A
sealing member 303 of an elastic material is in the form of a
rubber plug.
[0054] When the ink container is mounted to the ink jet head, as
shown in FIG. 4, the sealing member 303 at the bottom of the ink
container 10 is penetrated through a pipe 204 at and of the supply
unit 208, by which the ink can be supplied to the ink jet head from
the ink absorbing material in the ink container.
[0055] Since the sealing member 303 is used, the sealing can be
maintained when the pipe 204 of the supply unit 208 needles, so
that the electric contact or the like are not contaminated.
[0056] The supply unit 208 is provided with an ink supply passage
210 for fluid communication with the nozzle 215 and the pipe 204
coupled with the sealing member 303 of the color ink container
10.
[0057] In the ink supply passage 210, there is provided a filter
chamber (filter box) 211 having therein a stainless steel filter
213 as a nozzle clogging preventing means by trapping foreign
matters in the ink.
[0058] The filter box 211 has a cross-sectional area larger than
the ink supply passage 210. Therefore, the flow rate per unit area
through the filter is made smaller than the flow rate per unit area
in the ink passage to prevent adverse influence of the pressure
drop by the filter to the ink supply function even if the ink flow
rate is increased due to the high speed recording.
[0059] The filter 213 in the filter box 211 is disposed, crossing
the ink flow line, and substantially divides the filter box 211
into equal two parts.
[0060] For the purpose of simplicity of explanation, the ink supply
passage 210 is assumed to be constituted by an ink passage 210a for
fluid communication between the ink pipe 204 and the filter box
210, and an ink passage 210b for fluid communication between the
filter box 210 and the nozzle 215.
[0061] With this structure, as described hereinbefore, the bubbles
introduced through between the ink container 10 and the pipe 204
upon the ink container exchange, or the bubbles resulting from the
solved gases, enter the ink supply passage 210a, and the bubbles
can be concentrated on the filter in accordance with the ink supply
to the ink jet head.
[0062] In this embodiment, in order to remove the bubbles
concentrated on the filter, the sucking recovery mechanism for
removing the clogging is used, but the sucking capacity is 60 kPa
of the peak sucking pressure, and 300 mm.sup.3 of the sucking
quantity (total of yellow, magenta, cyan and black inks).
[0063] The filter 213 has a mesh of 8 .mu.m of the effective
transmission size and 44 mm.sup.2 of the cross-sectional area. The
pressure drop between the filter 213 to the nozzle is approx. 75%,
and the pressure difference across the filter 213 is approx. 15
kPa.
[0064] When this mesh of the filter 213 is used, the minimum
threshold pressure for transmittance of the bubbles is approx. 18
kPa. Therefore, the bubbles do not pass through the filter during
the normal recovery operation. The bubbles are permitted to pass
through the filter only when the filter 213 is closed by the
deposition of bubbles with the result that the effective area so
reduces and the ink flow rate per unit area so increases that the
pressure difference exceeds 18 kPa. Assuming that there is no
variation of the pressure of the ink supply passage, the 18 kPa
pressure is reached, when the bubbles cover 1/6 of the effective
filtering area. Therefore, the formation of the fine bubbles upon
the recovery operation in this embodiment occurs most when the
bubbles cover more than 1/6 of the filter. The description will be
made as to the detailed structure of the filter for suppressing
instability of the ink supply performance attributable to the fine
bubbles.
[0065] Since the ink has a substantial viscosity, the pressure
applied to the bubbles stagnating in the filter (pressure
difference across the filter) is highest on a line connecting the
inlet port and the outlet port. In this embodiment, the structure
is such that the bubbles are removed from the line.
[0066] FIG. 5 is an enlarged sectional view of the filter box 211
in the embodiment of FIG. 4. As described hereinbefore, the ink
supply passage 210a introduces the ink from the ink container into
the filter box through the inlet port 216. The ink is filtered by
the filter 213, and flows into the ink passage 210b in fluid
communication with the nozzle through the outlet port 217. In this
embodiment, the filter box is so disposed that the ink flow is
codirectional with the gravity.
[0067] As shown in FIG. 5(a), a recess 219 is formed on an inner
wall 212 having the inlet port 216 which is in the ink container 10
side of the filter box 211. The recess is formed at a position most
remote from the inlet port of the filter box. Therefore, the
distance between the inner wall surface and the filter 213 is
enlarged by the recess.
[0068] In FIG. 5(a), the recess is formed at a part of the marginal
area. The recess 219 may be formed covering the entire marginal
area, as shown in FIG. 5(b).
[0069] With the structures of FIG. 5(a) and (b), even if the
bubbles enter the ink supply passage upon the ink container
exchange with the result that the ink stagnates in the neighborhood
of the inlet opening of the filter box in accordance with the
supply of the ink to the nozzle, the bubbles move toward a position
where the distance between the filter 213 and the filter box is
large, because of the buoyancy of the bubbles and the surface
tension pending to reform the bubbles into light spherical
form.
[0070] Therefore, by the provision of the recess 219 at the
marginal area, the bubbles stagnate with stability away from the
opening. In this case, the flow of the ink for the ink supply
during the recovery operation, against the bubbles, is in the
direction crossing with the direction of the buoyancy, as
contrasted to the case that the bubbles are on the line connecting
the inlet port and the outlet port.
[0071] For these reasons, the deformation of the bubbles as in the
case where the bubbles exist in the central area of the filter,
does not occur, but at least a part of the bubbles existing between
the filter 213 and the internal wall surface having the inlet port,
passes through the filter 213 without formation of fine bubbles.
Additionally, the bubbles remaining in the filter box 211 are
positioned at the marginal area, and therefore, the ink flow during
the normal recording operation is not impeded.
[0072] In this embodiment, the structure of the recess at the
marginal area in the inner wall surface having the inlet port
function as bubble moving means for introducing the bubbles to the
marginal area.
[0073] FIG. 5(c) is a modification of this embodiment, wherein the
inner wall surface 222 having the inlet port 216 is so inclined
that the space from the filter 213 increases toward the marginal
area. The distance from the filter is the maximum at the most
remote position from the inlet port. In other words, the internal
wall surface extends inclinedly relative to a horizontal direction
perpendicular to the direction of the gravity, so that the
neighborhood of the inlet port is the lowest on the basis of the
direction of the gravity. In this modification, the bubbles
concentrated adjacent the opening are more easily movable than the
foregoing embodiment.
[0074] As shown in FIG. 5(a), (b) and (c), by expanding the gap
between the filter 213 and the internal wall at the marginal area
from the gap between the inlet port and the filter 213, the bubbles
stagnating at the central portion of the filter can be moved to the
position where the action of the pressure produced by the ink flow
during the recording operation or the sucking recovery operation is
not so strong, and therefore, the local increase of the pressure
acting on the bubbles and the variations of the acting positions
due to the cooperation with the buoyancy of the bubbles as in the
central portion of the filter, are reduced, so that the production
of the fine bubbles can be prevented.
[0075] Even if the bubbles are concentrated during the recording
operation or the like, the bubbles grow up at the marginal area,
and therefore, it can be avoided that the bubbles plug the inlet
port 216 of the filter box or that the ink supply to the nozzle
changes, before the bubbles are permitted to pass through the
filter by the pressure during the sucking recovery process.
[0076] Even if the direction of the ink ejection is not vertical
(coaxial with the direction of the gravity), more particularly,
even if it is in the horizontal direction crossing with the gravity
direction, the movement of the bubbles forming the meniscus on the
filter, can be promoted.
[0077] As shown in FIG. 5(b) and (c), by minimizing the gap between
the inlet port and the filter, the bubble can move without
limitation to the moving direction, so that the ink jet head
mounting position can be determined with larger design latitude
which may permit use of a common ink jet head for various ink jet
recording apparatuses.
[0078] Embodiment 2
[0079] FIG. 6 shows a second embodiment of the filter. In this
Figure, the same reference numerals as in the first embodiment are
assigned for the elements having the corresponding functions, and
the detailed descriptions thereof are omitted for simplicity. FIG.
6(a) is a sectional view when the ink ejecting direction of the ink
jet head is coaxial with the direction of the gravity, and FIG.
6(b) is a sectional view when the ink ejecting direction is
horizontal crossing with the gravity direction.
[0080] In this embodiment, as shown in FIG. 6(a), both of the
filter 213 and the internal wall 212 at the ink container 10 side
of the filter box 211, are inclined approx. about 40 degrees
relative to the horizontal plane.
[0081] Therefore, both of the filter and the wall guide the bubbles
in addition to the tendency of the upward movement due to the
buoyancy of the bubbles 251 as in the foreign embodiment. Even if
the bubbles form meniscuses in the filter, the portion where the
bubbles are deposited on the filter can be easily changed, as
compared with the case that the filter extends horizontally, and
therefore, the upward movement of the bubbles at the filter is made
more easier, and as a result, the bubbles at the marginal area of
the filter box are stabilized.
[0082] The bubble moving function is provided irrespective of the
pose or inclination, since the filter in the filter box has an
angle relative to the horizontal direction, even if the ink jet
unit is rotated through 90 degrees to eject the ink in the
horizontal direction, as shown in FIG. 6(b).
[0083] The angle of the filter in the filter box relative to the
horizontal plane is preferably 30-60 degrees to permit motion of
the bubbles, but is further preferably 40-50 degrees in
consideration of the flow resistance and the effects provided with
a plurality of inclinations. In this embodiment, it is approx. 40
degrees.
[0084] In this embodiment, the bubbles are promoted to move away
from the ink flow along the line connecting the inlet port and the
outlet port of the filter box, so that the main component of the
ink pressure actable on the bubbles is substantially codirectional
with the filter, and therefore, the bubbles are not subjected to
such forces as are effective to urge the bubbles to the filters
thus remarkably changing the configurations of the bubbles as in
the case where the bubbles are at the central portion of the
filter.
[0085] Therefore, the force acting on the bubbles stagnating at the
filter is substantially uniform resulting from the pressure
difference across the filter, and therefore, the bubbles can pass
through the filter without formation of the fine bubbles. This
embodiment is particularly suitable when the direction of the
buoyancy of the bubbles are opposite from the main ink supply
direction in the filter portion.
[0086] Similarly to the foregoing embodiments, the flow of the ink
during the sucking process operation upon the container exchange or
the like and the recording operation, is not impeded by the
filter.
[0087] The inlet port functioning as the connecting portion with
the filter box 211 in the ink passage extending between the ink
container 10 and the filter box 211, is substantially at the
central portion of the filter box 211 in this embodiment. This is
done in order to provide the effects with a plurality of
inclinations including the inclinations shown in FIG. 6(a) and
(b).
[0088] If the inclination during use is limited, an opening in
fluid communication with the ink supply passage may be formed
outside the central area of the filter box. An example thereof is
shown in FIG. 7.
[0089] In FIG. 7, the positions of the opening 216 and 217 is lower
on the basis of the gravity direction. With this structure, when
the bubbles in the filter box move to the marginal area, the
distance from the opening is larger as compared with the foregoing
embodiment, and therefore, the variation of the ink supply quantity
in the recovery operation is less. When the structure of FIG. 7 is
used, the bubble moving function is provided effectively in the
case of the positions shown in FIG. 6(a) and (b).
[0090] Embodiment 3
[0091] In the third embodiment, a wettability of the internal wall
surface of the filter box is changed in order to stabilize the
pressure applied on the air bubbles by moving the bubbles 251 away
from the inlet port in the filter box. FIG. 8 is a sectional view
of the filter box 211 in the ink jet recording apparatus. Here, the
wettability of the inner wall surface 221 is higher than that in
the internal wall surface 220. In order to change the wettability,
a water repelling material is applied on the internal wall surface
220, by which the advancing contact angle is changed from 50
degrees to approx. 80 degrees. Preferably, the contact angle is not
less than 90 degrees. The internal wall surface 221 may be
subjected to hydrophilic treatment such as corona discharging
treatment or plasma ashing treatment or the like. When the bubbles
at the filter are enlarged to a certain degree, the ink tends to
move from the internal wall surface 220 to the wall surface 221
having higher wettability along the internal wall having the inlet
port 216 in fluid communication with the ink container 10 side of
the filter box 211, and therefore, the bubbles 251 move along the
internal wall 220.
[0092] Bubble moving means in this embodiment is in the form of the
different surface treatment of the internal wall surface. Only with
the surface treatment, the influence of the carriage scanning
movement during the recording operation is significant although it
is possible to move the ink to the marginal area. Therefore, it is
preferable to combine this embodiment with one or more of the
foregoing embodiments to promote the motion of the bubbles.
[0093] When the wettability adjacent the inlet opening is improved
by the combination with the surface treatment, the motions of the
bubbles from the inlet port of the filter box, is irreversible.
[0094] The present invention is particularly suitably usable in an
ink jet recording head and recording apparatus wherein thermal
energy by an electrothermal transducer, laser beam or the like is
used to cause a change of state of the ink to eject or discharge
the ink. This is because the high density of the picture elements
and the high resolution of the recording are possible.
[0095] The typical structure and the operational principle are
preferably the ones disclosed in U.S. Pat. Nos. 4,723,129 and
4,740,796. The principle and structure are applicable to a
so-called on-demand type recording system and a continuous type
recording system. Particularly, however, it is suitable for the
on-demand type because the principle is such that at least one
driving signal is applied to an electrothermal transducer disposed
on a liquid (ink) retaining sheet or liquid passage, the driving
signal being enough to provide such a quick temperature rise beyond
a departure from nucleation boiling point, by which the thermal
energy is provided by the electrothermal transducer to produce film
boiling on the heating portion of the recording head, whereby a
bubble can be formed in the liquid (ink) corresponding to each of
the driving signals. By the production, development and contraction
of the the bubble, the liquid (ink) is ejected through an ejection
outlet to produce at least one droplet. The driving signal is
preferably in the form of a pulse, because the development and
contraction of the bubble can be effected instantaneously, and
therefore, the liquid (ink) is ejected with quick response. The
driving signal in the form of the pulse is preferably such as
disclosed in U.S. Pat. Nos. 4,463,359 and 4,345,262. In addition,
the temperature increasing rate of the heating surface is
preferably such as disclosed in U.S. Pat. No. 4,313,124.
[0096] The structure of the recording head may be as shown in U.S.
Pat. Nos. 4,558,333 and 4,459,600 wherein the heating portion is
disposed at a bent portion, as well as the structure of the
combination of the ejection outlet, liquid passage and the
electrothermal transducer as disclosed in the above-mentioned
patents. In addition, the present invention is applicable to the
structure disclosed in Japanese Laid-Open Patent Application No.
123670/1984 wherein a common slit is used as the ejection outlet
for plural electrothermal transducers, and to the structure
disclosed in Japanese Laid-Open Patent Application No. 138461/1984
wherein an opening for absorbing pressure wave of the thermal
energy is formed corresponding to the ejecting portion. This is
because the present invention is effective to perform the recording
operation with certainty and at high efficiency irrespective of the
type of the recording head.
[0097] The present invention is applicable to an ink jet apparatus
using piezoelectric elements for ejecting the ink without use of
the electrothermal transducers.
[0098] As will be understood from the foregoing, according to the
present invention, the ink supply is not impeded but is stabilized
even if the bubbles are in the filter box, and in addition, the
sucking recovery operation can be carried out without producing
fine bubbles.
[0099] Additionally, the ink jet recording apparatus which can
enjoy the above advantageous effects irrespective of the mounting
pose or inclination of the ink jet head, can be provided.
Accordingly, the ink jet head can be made common for different ink
jet recording apparatus for different usage. Therefore, the cost
can be reduced.
[0100] While the invention has been described with reference to the
structures disclosed herein, it is not confined to the details set
forth and this application is intended to cover such modifications
or changes as may come within the purposes of the improvements or
the scope of the following claims.
* * * * *